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344

Front Plates.

s   II

! I

ia are to be marked from the tube plate; but those along the
flange are obtained by laying upon the latter a very thin steel
strip 7 prepared with marked holes, .and of the exact length of
the flange. After marking through, the flange holes may be
drilled in a Horizontal Drill, and the plate holes in a Radial
Drill. The holes for the stay bolts are marked off to dimension,
as shewn at u, Fig. 311, and drilled with clearance for the bolt.

II.  Front Tube Plate.—The Plate is first marked as at 8, and
part &a cut out by Band Saw.    The pieces ga are next drawn out
to a tapering wedge as at sl5 Fig. 311, after which the parts gfr
may be removed by Band Saw.     Flange gb to gauge;  anneal
and straighten.    Plane edges yd and ge to a bevel, trimming the
corners by chipping, and mill the flanged edge as before.    Set
out all the plate rivets as at w, v, and Y, Fig. 311, and the tube
holes.    Prepare a steel strip the exact length of the flange, and
pitch the rivets upon it; then mark through to the flange one
rivet in every six, leaving the corner rivets.    (N.B.—It should be
remembered that the corner rivets, where three plates overlap, are
always better drilled absolutely ' in position.')    Now drill all the
plate rivets under a Radial Drill, and the tube holes at the same
time, making first a small guide hole for the pin drill 10.    The
stay tube holes are made to tapping size, and the other tube holes
to gauge.    The flange holes are drilled in a Horizontal Drill, and
the stiffening plates (v, Fig. 311) marked from the tube plate and
drilled separately.

III.  Bottom Front Plate.—Whiten the plate as before; draw
centreline, line na, and strike curve lib.    Set out the centres
of the furnace holes, and strike a circle on each, smaller than the
flue by the flanging allowance.     Drill a small hole for drill
steadiment at the furnace centres, then lay the pkte on the drill
in Fig. 291, and take out the large hole by the trepanning tool 12.
Heat and flange, as at-13, each of the furnace Holes, and after
cooling lay on the marking table to test the» original lines, which
have drawn a little; so the curve i ib must be re-stnick, and cut
by band saw.    Flange to gauge, including the setting of the
flange ends; anneal and straighten.    Mark out line i id and cut
out with band saw; plane also the edge xxa.   If possible, give
the bevel at J when cutting, but if that is not convenient, finish